One of the most significant aspects about the oilseed industry is the fact that quality can be spoiled at any point from the field to the grocery store shelf. Once the quality is compromised, no amount of hard work and sophisticated techniques can restore what has been lost. Processors and end users take steps to ensure oil quality, and there are simple practices that producers and elevators can use as well to maximize sunflower quality.

Bin Preparation / Pest Control

Proper storage management of sunflower begins before they’re even harvested. It’s important to thoroughly clean and inspect bins for structural damage. Repair all cracks and crevices that would allow the weather or insects in. Also, clean and inspect the aeration system—buildups in the ducts are excellent harborage areas for insects, and will also obstruct air flow. Finally, when all cleaning and repairs have been completed, consider applying residual insecticide treatments, following label instructions, at least two weeks prior to using the bin.

Preventing Damage at Harvest

There are three key objectives at harvest:

Recover all the good seed. Field loss, whether in the crop or with equipment setup

or operation, poses not only an economic loss, but also reduces the amount of available sunflower oil.

Maintain high purity. Foreign material such as weed seeds and insect matter may

Minimize mechanical damage. Damaged seed will not bring top grades or produce

top quality sunflower oil.

These three objectives can be accomplished on the combine, or/and with an on-farm cleaner to remove foreign material from sunflower going into storage.

Sunflower left in the field after it is already mature is vulnerable to deterioration by weather and pests. Thus, it’s best to get a crop that is harvest-ready off the field and into a controlled environment as quickly as possible.

For best quality sunflower, start harvest when moisture levels are in the mid teens, and then dry quickly. It is important not to allow seed moisture to become too low (sunflower in the High Plains is particularly sensitive to this), which may result in more hull damage at harvest. The greater the hull damage, the more susceptibility of fungal infection in the seeds. Research has shown that harvesting with seed moistures of 5 - 7% resulted in 15 -18% hull damage, where as harvesting seed with a moisture of 9% resulted in less than 10% hull damage.

Seed Drying

Sunflower seeds will need drying before going into storage if they were harvested wetter than 10%. There are several benefits of drying harvested seed:

• Permitting harvest when desired

• Allows harvest of seed with higher moisture content, which will reduce seed shattering loss and loss from birds.

• Reduces dependency on weather

Research has shown that the method and effectiveness of drying sunflower seeds has a direct influence on oil quality characteristics. Since drying also costs money, it would make sense to dry the seed only to a moisture level that will improve storage stability, and does not risk deterioration of oil quality. Also, if seeds are over-dried, there will be an economic loss because of the reduced weight of the seed.

Ken Hellevang, extension agricultural engineer at North Dakota State University, recommends that oil sunflower should not be stored above 10% moisture during the winter, and 8% during the summer. Confection sunflower should not be stored above 10% moisture during the winter and 9% during the summer. Sunflower can be stored for short periods during cool weather at 12% moisture with adequate airflow to keep the seeds cool.

Drying Process of Seed

The rate at which sunflower seeds dry will be determined by several factors. The principal factors are: Seed moisture, air flow rate, air temperature, and relative humidity of incoming air.

An increase in the drying air temperature will increase the moisture carrying capacity and decrease the humidity. A general rule of thumb: For every 20°F increase in air temperature, the moisture carrying capacity will double, and the relative humidity will decrease to one-half of its original value. Chart #1 shows that for any given humidity, when the temperature increases, the sunflower moisture will decrease.

Remember that a moisture meter can be fooled by sunflower coming from a dryer with shells that are drier than the kernels inside. For example, a moisture meter may give a reading of 10%, then climb back up to 12% again the next morning. Moisture rebound can be estimated by placing a sample from the dryer in a covered jar and rechecking the moisture after 12 hours.

*Equilibrium is reached when the net moisture exchange between the seed and the air is zero.

Comparing Different Drying Systems

Grain dryers are categorized in a number of different ways, according to their drying method or airflow direction, such as cross-flow, counter-flow, and concurrent-flow. Listed below are some of the drying systems along with advantages and disadvantages each have.

Natural Air/Low Temperature

Advantages:

• Bins can be filled at the harvest rate.

• Little supervision required.

• Properly sized system may be more economical than a high-temperature dryer.

Disadvantages

• Limit on initial seed moisture that can be dried.

• Must have electrical power at each bin for fan motor.

• Need to leave on until moisture front is through entire bin.

Layer Drying (a variation of Natural Air/Low Temp Drying)

Advantage

• Seeds with higher initial moisture may be harvested as compared to seed moisture when using full bin drying.

Disadvantage

• Multiple bins will be needed or harvest schedule may be restricted.

High-Temperature Bin Drying

Advantages

• Drying rate is faster.

• Bin can be used for storage at the end of drying season.

Disadvantages

• Large moisture variation between individual seeds is possible. May not be uniform moisture throughout bin.

• Stirring may result in seed damage.

• Needs to be monitored.

Column Dryers

Advantages

• Fast with relative uniform grain moisture.

• Available on most sunflower farms or local elevators.

• Dryer doesn’t occupy seed storage space.

• Flexibility of being able to move from one location to another.

• Not as dependant on outside air temperature and humidity.

Disadvantage

• Needs to be monitored consistently to avoid fire

• Dryer should be faced so fresh air intake is toward prevailing winds and away from fines produced from handling

• Efficiency not as good as in deep-bed drying

These are just a few of the more common types, but there are many others that will work. Remember again that top quality sunflower oil can only be produced from seed that has been properly dried: Drying too little or too much can result in lower quality seed.

The maximum recommended drying temperature of air used for drying varies by drying method, but it is typically 120 degrees for a bin batch dryer; 180 degrees for column batch; and 200 degrees for continuous flow/recirculating batch.

Always remember that sunflower is an oil-based crop, and fine fibers from sunflower seeds pose a constant fire hazard. Good housekeeping practices that prevent the accumulation of fines should be adhered to, and it’s always a good idea to have a fire extinguisher on hand when harvesting and drying sunflower.

Seed Storage

Remember that storage life of the seeds is not unlimited. It is critical to use proper aeration to cool seed and prevent seed deterioration.

The ideal temperature for insect and mold growth in stored grain is about 80 degrees. Cooling grain below 70 degrees reduces insect reproduction, and cooling it below 50 degrees causes insects to become dormant. Mold growth is almost nil at temperatures below 40 degrees. Hellevang recommends that grain should be cooled to about 20 to 25 degrees for winter storage, or as close as climate allows.

Because about a 20-degree temperature differential in the grain mass will cause moisture migration, aeration should start before the average outdoor temperature is 20 degrees cooler than the grain temperature. If stored sunflower is at 40 degrees and it’s 20 degrees outside, you need to cool down the sunflower in storage to take advantage of the cooler outside environment, Hellevang advises.

Cooling gradually in 10 to 15-degree steps to avoid a large difference between the bin and outside temperature, along with adequate bin vents, will help minimize condensation. Make sure bin roof openings are adequate: One square foot of bin vent opening for every 1,000 cfm of airflow is recommended.

Monitoring the moisture and temperature of seed in storage is critical to preserving seed quality. Check the condition of stored grain about every two weeks while grain is cooling, then about monthly after grain has cooled. A check should include measurements of moisture content and temperature at several locations.

Quality Assurance

Better sunflower seed quality results in enhanced value to the producer and the elevator, and higher quality sunflower seed oil for the downstream processors and consumers. The business world has a phrase for maintaining product from producer to end user: Quality Assurance. We can sum up key ways in which sunflower quality can be assured, as much as possible, in these five steps:

If bird pressure is severe, disease levels are high, or lodging problems are occurring, the use of a harvest-aid desiccant for sunflower may be considered when the crop is mature and an early harvest would be an advantage.

Early drydown of sunflower plants may also slow or stop development of head rot and reduce sclerotia and destruction of seeds. However, warm sunny days following a desiccant application is needed to give the best results. Grower experience indicates head rot may actually get worse when wet weather follows desiccation compared to green fields left untreated. Thus, weigh the weather probabilities and the advantage of early harvest compared to the risk of wet weather following desiccation.

Desiccation can also reduce head shattering, control weeds (especially large weeds like kochia and marshelder, resulting in less dockage and less wear and tear on combines) and ease crop drying with reduced drying costs.

Two types of desiccants can be used. These include paraquat (Gramoxone Extra) and sodium chlorate (Defol) for use on oilseed and confectionary sunflower. Allow a minimum of 7 to 10 days prior to harvest to get maximum killing and drydown of the sunflower. Read and follow the label for rates and adjuvants to use.

Apply desiccant by air after the back of sunflower heads have turned yellow and the bracts are turning brown. Physiologically mature sunflower plants have a seed moisture content between 33 and 35%. Some sunflower hybrids now have a stay-green stalk characteristic, so go by the heads or seeds. Another way to tell if physiological maturity has occurred is to rub the chaffy material on the front of a sunflower head. If it rubs off easily, the plant is physiologically mature.  Duane Berglund, North Dakota State University extension agronomist